The latest issue of MuntInfo/MonnaieInfo (the Belgian Mint's magazine) is now online, and provides some more info about this coin. Seems that it is indeed colored, not plated. Here is a rough and slightly abridged translation of the relevant part:
The new coin, designed by Luc Luycx, was inspired by the designs that Marcel Rau created for the 20 and 50 c bronze coins in the 1950s. This choice does not only remind of the time when the accident happened.
(Note: Rau's circulation coins were designed and first issued in the early 50s, before the accident, C.F.) It is also an hommage to all the miners who have worked to improve our standard of living, and in this case even lost their lives. The maximum mintage is 50,000 coins. Only a few of these will be made in a special version where Rau's miner on the obverse is colored.
MuntInfo 41 - Dutch/Flemish version:
http://treasury.fgov.be/intermunt/MUNTINFO/MI-41%20NL.pdfMonnaieInfo 41 - French/Walloon version:
http://treasury.fgov.be/intermunt/MUNTINFO/MI-41%20FR.pdf(By the way, the piece on the front page is not a coin but a medal which will be part of the 2006 mint sets.)
Christian